 /*******************************************************************************
  * Copyright (c) 2000, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.internal;

 import org.eclipse.core.runtime.ListenerList;
 import org.eclipse.core.runtime.Platform;
 import org.eclipse.jface.util.SafeRunnable;
 import org.eclipse.jface.viewers.ISelection;
 import org.eclipse.ui.INullSelectionListener;
 import org.eclipse.ui.ISelectionListener;
 import org.eclipse.ui.IWorkbenchPart;

 /**
  * Provides per-part selection tracking for the selection service.
  */
 public abstract class AbstractPartSelectionTracker {
     /**
      * List of selection listeners for this tracker
      */
     private ListenerList fListeners = new ListenerList();

     /**
      * List of post selection listeners for this tracker
      */
     private ListenerList postListeners = new ListenerList();

     /**
      * The id of the part this tracls
      */
     private String fPartId;

     /**
      * Constructs a part selection tracker for the part with the given id.
      *
      * @param id part identifier
      */
     public AbstractPartSelectionTracker(String partId) {
         setPartId(partId);
     }

     /**
      * Adds a selection listener to this tracker
      *
      * @param listener the listener to add
      */
     public void addSelectionListener(ISelectionListener listener) {
         fListeners.add(listener);
     }

     /**
      * Adds a post selection listener to this tracker
      *
      * @param listener the listener to add
      */
     public void addPostSelectionListener(ISelectionListener listener) {
         postListeners.add(listener);
     }

     /**
      * Returns the selection from the part being tracked,
      * or <code>null</code> if the part is closed or has no selection.
      */
     public abstract ISelection getSelection();

     /**
      * Removes a selection listener from this tracker.
      *
      * @param listener the listener to remove
      */
     public void removeSelectionListener(ISelectionListener listener) {
         fListeners.remove(listener);
     }

     /**
      * Removes a post selection listener from this tracker.
      *
      * @param listener the listener to remove
      */
     public void removePostSelectionListener(ISelectionListener listener) {
         postListeners.remove(listener);
     }

     /**
      * Disposes this selection tracker. This removes all listeners currently registered.
      */
     public void dispose() {
         synchronized (fListeners) {
             Object [] listeners = fListeners.getListeners();
             for (int i = 0; i < listeners.length; i++) {
                 fListeners.remove(listeners[i]);
                 postListeners.remove(listeners[i]);
             }
         }
     }

     /**
      * Fires a selection event to the listeners.
      *
      * @param part the part or <code>null</code> if no active part
      * @param sel the selection or <code>null</code> if no active selection
      * @param listeners the list of listeners to notify
      */
     protected void fireSelection(final IWorkbenchPart part, final ISelection sel) {
         Object [] array = fListeners.getListeners();
         for (int i = 0; i < array.length; i++) {
             final ISelectionListener l = (ISelectionListener) array[i];
             if ((part != null && sel != null)
                     || l instanceof INullSelectionListener) {
                 Platform.run(new SafeRunnable() {
                     public void run() {
                         l.selectionChanged(part, sel);
                     }
                 });
             }
         }
     }

     /**
      * Fires a post selection event to the listeners.
      *
      * @param part the part or <code>null</code> if no active part
      * @param sel the selection or <code>null</code> if no active selection
      * @param listeners the list of listeners to notify
      */
     protected void firePostSelection(final IWorkbenchPart part,
             final ISelection sel) {
         Object [] array = postListeners.getListeners();
         for (int i = 0; i < array.length; i++) {
             final ISelectionListener l = (ISelectionListener) array[i];
             if ((part != null && sel != null)
                     || l instanceof INullSelectionListener) {
                 Platform.run(new SafeRunnable() {
                     public void run() {
                         l.selectionChanged(part, sel);
                     }
                 });
             }
         }
     }

     /**
      * Sets the id of the part that this tracks.
      *
      * @param id view identifier
      */
     private void setPartId(String partId) {
         fPartId = partId;
     }

     /**
      * Returns the id of the part that this tracks.
      *
      * @return part identifier
      */
     protected String getPartId() {
         return fPartId;
     }

 }

